It is known in the art of hemodialysis and other blood treatment machines using measured values of certain parameters in order to control the working of the machine.
For instance, EP097366 and U.S. Pat. No. 4,508,622 both disclose a device provided with two conductivity cells 32,50 on the dialysis liquid side; one cell operates upstream the dialyzer and the other downstream the dialyzer. The two cells are able to measure conductivity of the dialysis liquid or sodium concentration. The measured data of detectors are compared and eventually used to control the composition of the dialysis solution.
In Gambro EP0330892, it is of advantage to employ measured values of a patient's conditional values to control functional aspects of hemodialysis equipments. In this fashion, the hemodialysis equipment may be controlled dependently of specific treatment requirements of a patient. In particular, this reference teaches to determine the concentration for a certain solute in patient's blood and other important parameters as actual clearance (indicated herein as K in ml/min) or dialysance values (expressed herein as D in ml/min). If for instance the system of EP0330892 is adapted for determining sodium concentration or conductivity of patient's blood, the dialysis liquid concentration can be controlled in order to bring about an equilibrium between the conductivities of blood and dialysis liquid, thereby obtaining a control adapted to the individual which should provide comfort for the patient.
It is also known from EP0532433 a blood treatment device able to detect actual sodium dialysance and then derive urea clearance by extrapolation. Such a calculated urea clearance is then compared with a desired urea clearance value and in case of need the flow rate of the dialysis pump or of the blood pump, or the treatment time are changed. In case treatment time is changed also the UF rate of the ultrafiltration pump is modified.
On the other hand during the last twenty years a specific index, the KT/V index, has been regarded as particularly indicative of the dialysis treatment. More in detail Keshaviah and Collins (Keshaviah P, Collins A: Rapid high-efficiency bicarbonate hemodialysis, Trans Am Soc Artif Intern Organs 32: 17, 1986) reported in a well documented and well designed study on short dialysis, using the KT/V index as a parameter of dialysis adequacy. This index, introduced in 1985 by Gotch and Sargent (Gotch F, Sargent J A: A mechanistic analysis of the National Cooperative Dialysis Study (NCDS). Kidney Int. 28: 526, 1985) is calculated as the product of the urea clearance (K, ml/min) of the dialyser and duration of the dialysis session (T, min), divided by the distribution volume of urea (V ml). Gotch and Sargent analysed the data of the large scale National Cooperative Dialysis Study (NCDS) in the US and determined that a KT/V value of 0.9-1.0 constitutes adequate dialysis therapy. Values less than 0.8 are associated with a high probability of therapy failure. Keshaviah and Collins (Keshaviah P, Collins A: Rapid high-efficiency bicarbonate hemodialysis, Trans Am Soc Artif Intern Organs 32: 17, 1986) also demonstrated that short and rapid dialysis treatment is well tolerated when acetate is replaced by bicarbonate and is not associated with increased mortality and morbidity if therapy is prescribed keeping KT/V greater than 1.
In view of the above works, the value D or K for a certain solute (Notice again that Durea=Kurea) have been employed to determine value K*Ti, herein indicated as dialysis dose achieved after time Ti.
The approach presently followed in the blood treatment machines available on the marketplace is to obtain a measure of and to provide information related to a total dialysis dosage K*T value delivered as time progresses during a hemodialysis treatment procedure. This measure and the information provided is essentially based on parameters including:                a prescribed duration of the treatment procedure,        the blood flow rate,        the choice of the hemodialyser        
A combination of above parameters is employed to obtain a measure of the total dialysis dosage value K*Tt delivered as an integral of mean measured instantaneous clearance values measured after determined time increments, the dialysance of the chosen dialyser (which is an in vitro clearance value) and the effective treatment time. The effective treatment time is the time during which diffusive (and generally also convective) transfer of blood solutes across a semi-permeable membrane of a hemodialyser takes place.
The above procedure basically enables a measure to be made of the K*T value delivered to a patient during a hemodialysis treatment procedure.
At the end of the treatment which normally lasts a prefixed total time Ttot, the machine provides the user with the value of K*Ttot and with the value K*Ttot/V.
This procedure, however, suffers from a number of drawbacks. Specifically, such factors as blood flow rate and effective treatment time, which are relevant to clearance, are prone to change or are difficult to follow during a hemodialysis treatment procedure. Furthermore, the dialysance or clearance capacity of hemodialyser products can change significantly during a hemodialysis treatment procedure time. Present day hemodialysis monitoring equipment and hemodialysis procedure methods may comprise means for assessing or measuring dialysis dosages delivered to a patient over determined time increments, but no means are available for controlling the dialysis dosage value actually delivered to the patient, on an ongoing bases during treatment, and for carrying out actions on the dialysis machine working parameters as a function of the detected dialysis dosage delivered to the patient.
It is an overall objective of the present invention to secure an ongoing control over the actual total dialysis dosage delivered to a patient.
It is another object of the invention to control some parameters of a blood treatment machine as a function of the values of the dialysis dose measured in the course of the treatment.
Furthermore, it an object of the invention to provide a control apparatus and a blood treatment equipment able to coordinate achievement of the prescribed dialysis dose with substantially contemporaneous achievement of other prescription(s).
A further object is to provide a system for synchronizing achievement of a prescribed dialysis dose, of a prescribed weight loss and of a further prescribed prescription, such as concentration of a certain substance in patient's blood.
Another object of the invention is to offer a system, which is adapted to reduce, if possible, the treatment time while achieving the requested prescribed results at the end of the treatment.
Moreover it is an object of the invention to provide a controller and an equipment using said controller able to display updated values for a number of parameters, on ongoing basis at regular intervals during treatment.